1. Field of the Invention
The present invention relates to an easy adhesion film used as a base film for a transparent conductive film suitably utilized for a touch panel, etc. In particular, it relates to an easy adhesion film capable of improving the durability in terms adhesive property, for instance, of a transparent conductive thin film made of indium tin oxide or the like to the base film.
2. Related Art
In recent years, liquid crystal displays have come into the spotlight as image display devices. They are seen to have high potential for application to portable electronic notebooks, information terminals and so forth. As input devices for portable electronic notebooks, information terminals and so forth, transparent touch panels overlaid on a liquid crystal display element, especially resistance-film-type touch panels, are widely used because of their low cost and so forth.
The resistance-film-type touch panel generally consists of a transparent conductive film and a glass plate overlaid with a transparent conductive thin film disposed across an appropriate gap. The transparent conductive films are generally produced by forming a transparent conductive thin film of indium tin oxide (hereinafter referred to as ITO) or the like on a transparent polymer film.
The transparent polymer film used for a transparent conductive film has a large number of fine irregularities (unevenness) on its surface. The irregularities are formed by embossing so as to have a certain range of arithmetical mean deviation and maximum height in order to prevent occurrence of Newton rings when the touch panel is touched (pressed)(Japanese Unexamined Patent Publication No.08-077871 (1996)).
A transparent conductive film using such a transparent polymer film as a substrate can not produce sufficient adhesion between the transparent polymer film and the transparent conductive thin film. This leads to poor durability, for instance peeling or abrasion, of the transparent conductive thin film when used for the touch panel.
Therefore, an object of the present invention is to provide a film having sufficient durability when provided with a transparent conductive thin film and suitable for forming a transparent conductive thin film having transparency and anti-Newton ring property.
The inventors conducted an extensive study to achieve the above-mentioned object. As a result, they found that an easy adhesion film for a transparent conductive thin film having all of the desired properties, such as adhesion with a transparent conductive thin film, transparency and anti-Newton ring property can be obtained by providing on a transparent polymer film a resin layer comprising a specified resin binder and resin particles admixed with an ionizing radiation curable resin binder.
An easy adhesion film for a transparent conductive thin film of the present invention comprises a transparent polymer film and an easy adhesion layer formed on the transparent polymer film, wherein the easy adhesion layer comprises at least an ionizing radiation curable resin binder, a (meth) acrylate copolymer binder and polymethyl methacrylate resin particles.
According to the present invention, an easy adhesion film for a transparent conductive thin film having high durability can be provided. In addition, transparency and anti-Newton ring property can be obtained when provided with a transparent conductive thin film.
A transparent conductive film is usually thermally shrunk by heat treatment called annealing in order to prevent shrinkage after assembly into a touch panel. During this annealing process, oligomer precipitation from a transparent polymer film becomes a problem because it causes degradation of transparency. The easy adhesion film for a transparent conductive thin film of the present invention does not suffer from such degradation of transparency.